Image scanners, copiers, facsimile machines and other electronic imaging devices provide images in an electronic form suitable for transmission, printing or storage. In a typical image scanner or copier, light from a document or other image source is focused onto linear arrays of photosensors for scanning one line at a time. A two dimensional image is scanned by providing relative movement between the linear sensor arrays and the original image. In some scanning mechanisms, a line from a document is focused onto a sensor array having an overall length that is much shorter than the length of the line being scanned. For scanners with small sensor arrays, the light path is folded by mirrors to accommodate the focal length of an optics system. In other scanning mechanisms, the sensor array length is substantially the same as the line being scanned. For either type of sensor array, there is a need for a system for moving the sensor array relative to the document or other image while maintaining a precise alignment of the sensor array relative to the document or other image being scanned.